The highest mountain is located on Mars. The giant volcano Mount Olympus is the highest mountain in the solar system and in the known universe. At 14 miles and 388 miles across, it is almost three times the height of Mount Everest and so wide that its base would cover Arizona, or the whole of the area of the British Isles. The crater on the top is around 45 miles wide and over nearly 2 miles deep, easily big enough to swallow London.

We traditionally measure mountains by their height. If we measured them by their size, it would be meaningless to isolate one mountain in a range from the rest. That being so, Mount Everest would dwarf Olympus Mons. It is part of the gigantic range which is nearly 1,500 miles long.